1. Field of the Invention
The present invention is directed to an AC current electromagnetic relay, more particularly, to an AC current electromagnetic relay with a flat pivoting armature and a generally E-shaped yoke.
2. Description of the Prior Art
Electromagnetic relays with a flat pivoting armature and a generally E-shaped yoke are known, for example, as disclosed in U.S. Pat. No. 3,553,729. In the relay, a U-shaped flat armature is pivotally supported on an E-shaped yoke having center and side legs of equal length so as to complete the magnetic circuit with a coil disposed around the center leg serving as a core. The U-shaped armature having a pair of parallel arms connected by a web is placed on the yoke with the free end edges of the arms pivoted on the side legs at the intermediate portions along its length, so that upon the energization of the coil the armature is pulled toward the yoke surface to be in set position where it is in parallel with the yoke surface to have the web brought in abutting contact with the free end portions of the respective ones of the three legs of the yoke. In the meanwhile, the E-shaped armature is difficult to be formed into accurate configuration in which the free end portions of the respective legs are positioned exactly in the same plane and thus frequently suffers the misalignment in the direction perpendicular to the yoke surface. In view of the fact that the contacting portions of the legs with the yoke is arranged in a line, such misalignment will certainly lead to unstable contacting engagement between the armature and the yoke, rendering the armature to chatter and therefore unstable contacting operation. This is particularly disadvantageous when the relay is to be driven by AC current since the above unstable or uncertain contacting engagement between the armature and the yoke is very susceptible to fluctuation of magnetic flux in the yoke, although the fluctuation being reduced to a minimum by a suitable shading ring used around the core, so that the armature will chatter at the time of energizing the coil to produce unacceptable beating action.